Functional Capacity in Patients of Severe and Mild Postural Orthostatic Tachycardia Syndrome

Abstract

Introduction Postural orthostatic tachycardia syndrome (POTS) is a form of dysautonomia presenting with palpitations, lightheadedness, brain fog, headaches, and fainting¹. Several tests are used in POTS workup. Most important is the Tilt Table Test. POTS is diagnosed as change of 30 beats per minute(bpm) or more in adults and 40 bpm in people less than 18 or heart rate greater than 120 bpm within 10 minutes of head-up tilt table test. Metabolic stress test is done in patients of POTS to measure the performance of heart and lungs during physical stress². Functional capacity (FC) in this test indicates the ability of heart to cope with stress.The aim of this study is to measure functional capacity in mild and severe POTS patients and compare both groups Methods We analysed the POTS patients retrospectively. Inclusion Criteria POTS patients who underwent tilt table test during their workup, were included. Experimental Group Those having a change of 50 bpm or greater in heart rate during tilt table test were included in this group and termed as severe POTS patients, consisted of 124 patients. Control Group It comprises 136 patients having heart rate changes between 30 to 50 during tilt table test and termed as mild POTS patients. Functional capacity (FC) of these patients was taken from metabolic stress test. FC above 80% was considered normal, between 60% to 80% mildly reduced and below 60% as severely reduced. RESULTS Out of 124 patients in the experimental group (severe POTS), 61(46%) patients have severely reduced FC and 43(35%) patients have mildly reduced FC. While out of 136 patients in the control group, 46(34%) patients have severely reduced FC and 56(41%) have mildly reduced FC. p-value between the two groups is 0.0317